1. Field of the Invention
This invention relates to an injection molding unit for processing synthetic materials, comprising a changing device being supplied with synthetic materials and a plurality of connecting bores. The connecting bores are transversally lockable by means of separately triggerable stoppers, for optional connection of supply lines, from which material stored in tanks of the inflection molding unit is supplied via a feed opening.
2. Description of the Prior Art
U.S. Pat. No. 4,731,005 discloses a unit of this type with a changing device in which several supply lines are disposed side by side on a guide rail that extends transversally with respect to an injection axis. These supply lines serve to optionally supply the injection molding unit either with synthetic material or with cleaning material. The individual supply lines are carried by a sliding plate and alternately conform with the feed opening of the carrier block by means of a ball rolling spindle, which engages in mentioned sliding plate. Due to the fact that the stoppers are brought in line with a coupling element during the transversal displacement, as a result, they are triggerable perpendicularly with respect to a drop hole, which is arranged in the carrier block. Due to the transversal displacement of the supply lines, necessary for the feeding of material, and the vertical displacement of the stoppers effected for it, however, a large space over the machine has to be kept free for the supply units and is even increased by the flexible feed lines required.
A further changing device comparable with the aforementioned changing device is known from U.S. Pat. No. 4,889.479. In this device the transversal displacement of the supply lines is managed by interconnected hydraulic cylinders, simplifying achievement of the final and intermediate positions. Separate hydraulic facilities arranged in the area of the changing device are also known from U.S. Pat. No. 5,022,847.
Another possibility to supply synthetic material via supply lines is, for example, to effect the transport by an airflow by means of a dosification appliance, as for instance is known from U.S. Pat. No. 3,980,208. However, it is also possible to arrange different supply tanks radially around the feed shaft, as for example is known from U.S. Pat. No. 4,418,845.